1. Field of the Invention
The present invention relates to an air nailing gun adapted to drive U-nails into a post or the like to fasten a cord member to the post and, more specifically, to a hammer head assembly for use in such an air nailing gun.
2. Description of the Related Art
In ranches or barns, people may set up wooden posts 4 around the boundary, and then fasten steel ropes 5 to the posts 4 with U-nails 2 to build a fence (see FIG. 3). However, it is not easy to drive U-nails 2 into wooden posts 4 accurately. Because there isn""t any tool specifically designed for driving this kind of U-nails into wooden materials, people usually use a hammer to drive this kind of U-nails into wooden materials. However, because the two pointed ends respectively sloping outwards, they tend to be deformed when driving into the workpiece. Further, during hammering, the hammer may strike against the fingers holding the U-nail accidentally, causing an injury.
The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a hammer head assembly for air nailing gun, which is specifically designed for driving U-nails into wooden materials. It is another object of the present invention to provide a hammer head assembly for air nailing gun, which positively holds the loaded U-nail in position for driving. To achieve these and other objects of the present invention, the hammer head assembly comprises an externally threaded, stepped, hollow, cylindrical mounting base fastened to the air nailing gun, the mounting base having a center through hole axially extended through top and bottom ends thereof for the passing of the striking rod of the air nailing gun; a sliding sleeve inserted into the center through hole of the mounting base and partially extended out of the bottom end of the mounting base, the sliding sleeve having a center through hole axially extended through top and bottom ends thereof for the passing of the striking rod of the air nailing gun, and an outward stop flange extended from the periphery of the bottom end thereof; a first spring member mounted in the mounting base and adapted to impart a forward pressure to the sliding sleeve; a coupling nut sleeved onto the sliding sleeve and stopped above the outward stop flange of the sliding sleeve outside the mounting base, the coupling nut having an inner thread; a nail holder adapted to hold a U-nail for fastening, the nail holder having an outer thread threaded into the inner thread of the coupling nut, a flat receiving slot extended to a bottom side thereof and adapted to receive a U-nail for fastening, and a top insertion hole disposed in a top side thereof in communication with the flat receiving slot; a hammer rod mounted in the sliding sleeve and aimed at the top insertion hole of the nail holder for driving by the striking rod of the air nailing gun to force a loaded U-nail out of the nail holder into a wooden material; and a second spring member mounted inside the sliding sleeve and adapted to push the hammer rod toward the striking rod of the air nailing gun.